One problem here is that the use of the ablative ("primā viā") is then unclear. You can't just use the bare ablative to mean "on the road", but rather it'd have to be "in primā viā". Instead, if you take "primā viā" as an instrumental, you get "using the first road", and then it (hopefully!) becomes clear that what's being joined is the cities, since you can use roads to join cities, but using them to join people is a bit of an odd concept.

I'm also not sure the preposition "ex" can be used that way. In particular, I'm not sure if the Romans would express "the man from the city" as "homō ex urbe" -- I think they'd more likely use the genitive, "homō urbis", or if the context is appropriate, a full relative clause like "homō quī vēnit ab urbe" ("The man who came from the city").